Device for supporting and handling loads by means of vacuum operated suction pads

ABSTRACT

A device can be applied to a lifting and/or transporting unit for the controlled support of loads by generating a vacuum in one or more suction pads. The device includes a vacuum gauge measuring the vacuum level in at least one of the suction pads and safely controlling movement of the device. A safety system prevents erroneous dropping of the suspended load. The suction pads for gripping the load can be mounted on a holding frame which can be changed and/or lengthened for accommodating various types of loads.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device which can be applied to alifting and/or transporting unit for controllably supporting andhandling loads by generating a vacuum in one or more suction pads.

2. Description of the Prior Art

The operation of lifting and supporting a load by means of suction padsin contact with a surface of the loads and in which a vacuum isgenerated is a well known and used technique, especially, for transportpurposes inside working areas and therebetween. Known devices of thiskind are very simple and usually include, in addition to the suctionpad(s) and a vacuum source, means for controlling the connection of thesuction pads to the vacuum source or to atmosphere only.

However these known devices have various drawbacks, both during the loadgripping step for lifting and transporting the load and during thelatter operation. In fact, these known devices do not possess a controlto ensure that a sufficient vacuum level has been reached within thesuction pads at the time the operator leaves the load to the lifting andtransporting unit to which the supporting device is applied. This leadsto human errors and requires a certain skill by the operator who mustoperate the lifting and transporting unit only once a sufficient vacuumlevel has been reached within the suction pads, but without an excessivetime delay for obvious productivity reasons.

However, the greatest drawback of the known supporting devices withsuction pads is that they do not include a safety system against anuncontrollable rapid decrease of the absolute vacuum level within thesuction pads during the load lifting and/or transporting operation. Suchvacuum decrease can occur for various reason, particularly in case offailures of the vacuum generation and transmission system or elsebecause of unforeseen porosity of the surface on which the suction padsare to be placed, or due to maneuvering errors by the operator whoerroneously can depress the load release button while the load is stilllifted or suspended.

Finally, another drawback of the known devices of this kind is that theyhave a fixed number of suction pads and/or a fixed arrangement thereofon the lifting tool, so that loads having different features cannot beaccommodated by a single device. There are, for example, loads having asmall thickness and a large surface which are to be transported edgewiseand therefore require that the suction pads be applied to their sidesurfaces, or loads having uneven surfaces requiring the application ofthe suction pads at different levels, and so on. Therefore, thesedifferences in the load features require the use of a different devicewhich, of course, results in a lifting device inventory of remarkablecosts.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a loadsupporting device of the above mentioned type, which obviates the abovedrawbacks of the known devices, while maintaining a very simple andinexpensive structure that will ensure the greatest possible safety forthe operator as well as great versatility.

These characteristics are substantially attained in a device of theabove mentioned kind in that it includes a vacuum gauge measuring thevacuum level within at least one of the suction pads, and at least onetransducer to control at least one function of the lifting and/ortransporting unit in response to the at least one vacuum level measuredby the vacuum gauge.

Thus, it is possible to control different functions of the device,especially in such a manner that it will operate only when a presetvacuum level has been reached and, in case of a subsequent undesiredvacuum drop below a preset level, it automatically will cause the loadto be slowly lowered and/or an alarm signal to be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic showing of a device according to the inventionas applied to a particular load balancing unit;

FIG. 2 is an enlarged view of the portion of the device of FIG. 1 whichis designed to controllably support the load;

FIG. 3 is an elevation view, partially cut-away, of a detail showing asafety system against incidental load releases;

FIG. 4 is a partial side elevation view of the device of FIG. 1 providedwith a suction pad holder, partially cut-away and removed from thedevice;

FIG. 5 is a top plan view of the suction pad holder;

FIG. 6 is a sectional view taken along the line VI--VI of FIG. 5;

FIG. 7 is a side elevation view of the suction pad holder having thesuction pads secured to a frame pivotally mounted to a seat receiving asuction nozzle;

FIG. 8 shows a detail of a suction pad provided with a sensor; and

FIG. 9 is a circuit diagram of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, the device according to the invention can beapplied to a lifting and/or transporting unit which, in the particularcase here illustrated, includes equipment capable of balancing loads,generally indicated at 10 and including an upright 12 supporting anoverhanging horizontal beam 14. A load balancing assembly 18 canlongitudinally run on beam 14 by means of wheels 16, this assembly beingknown per se and substantially formed of an electric motor 20 deliveringa balancing torque to a roller on which a lifting cable 22 is wound andintended to directly or indirectly support the load.

Typically, a device 24 according to the invention is applied to thelifting cable 22, which is electrically connected, through an electriccable 26, to the balancing assembly 18 as well as pneumaticallyconnected, through a duct 28, to a vacuum unit 30 provided with a vacuumtank, known per se. Duct 28, which is held in position by a spring 32,is supported wound in loops by means of wheels 34 running along the beam14 and supporting also an electric cable 36 supplying the balancingassembly 18.

Alternatively, instead of providing a separate vacuum unit with tank 30,this unit can be embodied within the balancing assembly 18. Of course,in this case, since the vacuum unit with tank is of smaller dimensions,smaller flow rate values can be reached and therefore only loads havingeven and nearly impermeable surfaces can be lifted or balanced, whilehaving at all times the assurance that the vacuum in the suction padsslowly decreases in the case of a mechanical or power failure. Asanother alternative, the vacuum can be generated by a venturi operatingwith compressed air supplied by a compressor and this venturi could belocated either in the balancing assembly 18 or even within the device24.

The device 24, illustrated in more detail in FIG. 2, is secured to thelifting cable 22 by screws 38 and is connected to the duct 28 by meansof a plug 40. Its structural or body portion 42 includes controlling andoperating elements for the various functions of the device 24 andequipment 10 and transmits the weight of the load from a frame 44carrying suction pads 46 to the screws 38. The device includes also asensor 48 depending from its bottom surface and extending beyond thesuction pads 46 and held under the bias of a coilspring 50. The movementof sensor 48 causes a vacuum to be supplied into the suction pads 46.The level of this vacuum can be visually controlled by the operator atall times by means of a gauge 52 and is detected at all times by avacuum gauge 54 capable of controlling, through one or more transducers,an equal number of functions of equipment 10 once preset vacuum levelshave been reached within the suction pads 46. More particularly, andwith reference to the circuit diagram of FIG. 9, as the vacuum gauge 54indicates that a first vacuum level is reached, it supplies through afirst transducer T1 an operating or controlling signal to the equipment10, more particularly to the balancing assembly 18, which performs loadbalancing. In this particular case, the balancing occurs by means of areaction force, the value of which is set by the operator depressing oneof push-buttons 56, controlling respective potentiometers 58 which canbe calibrated to desired loads. Another potentiometer 60 controls thedevice weight balance.

Therefore, due to the first transducer T1, the vacuum gauge 54automatically controls the operation of the balancing assembly 18 sothat this balancing action exactly begins at the necessary time, namely,neither too early when an insufficient vacuum would be present, nor toolate when a time loss would occur.

The vacuum gauge 54 also controls a second transducer T2 supplyinganother signal when the absolute vacuum level falls below another presetvalue, which is lower than the first mentioned level. This situation canoccur when the device is operating under emergency conditions and thereis the danger that the load might fall. In order to avoid this danger,the signal supplied by the second transducer T2 energizes an alarmmember, a lamp 62 for example, and causes also slow load lowering sothat the load comes to rest before the vacuum level within the suctionpads falls below such a level that the load support is no longerassured. Of course, it is necessary that the second transducer T2 shouldoperate after the vacuum level is increased during the load grip, whichcan be obtained by subjecting the second transducer T2 to an operatingsignal which takes into account a certain time delay, e.g. provided by atimer T, at the beginning of the suction operation, or else the factthat the first transducer T1 must be first operated, or eventually thefact that the absolute vacuum level is decreasing.

In case of a regular operation, and in order to release the device fromthe load, after the latter has been slowly lowered by acting with thehands on the frame 44 or by depressing a suitable push-button 64, itwill be sufficient to depress a push-button 66 for causing suction padrelease. Of course, this push-button 66 disconnects the secondtransducer T2 to avoid unnecessary alarm signals.

To provide safety against the erroneous or inadvertent depression of thepush-button 66 by the operator when the device 24 is lifted from theground, in which case the load held by the suction pads wouldautomatically release and fall to the ground, the system illustrated inFIG. 3 is provided. It includes a cylindrical shaped body 110 having aportion 111 of smaller diameter forming with the body 110 a step 112.The smaller diameter portion 111 is fitted with clearance in acylindrical frame 113 secured to a top wall 114 of the device 24. A stopelement 116 is secured to the lower end of the smaller diameter portion111, which element together with the abutting surface formed by the step112, has the function of limiting the travel of body 110 within thecylindrical frame 113 secured to the lifting device 24.

The cylindrical body 110 is provided on the top with a cylindricalrecess 117 intended to receive the lifting cable of the lifting and/ortransporting unit, which is secured to the cylindrical body by screws115.

Electrical connection is made through a connector 127 secured to thebody 110 by means of a bridge 118 and a washer 119. The upper portion ofthe cylindrical body 110 is provided with axially extending recesses 121receiving springs 122 resting at their lower ends on the recess bottomsand secured at their upper ends to pins 123 passing through theassociated recesses and screwed at their inner ends in threaded holes124 provided in the cylindrical frame 113. The pins 123 are thusfastened to the frame 113 and therefore to the device 24. The lower endof the cylindrical body normally contacts an arm 125 of a microswitch126 connected to the various control elements in the device 24.

In the position shown in FIG. 3, the body 110 bears against thecylindrical frame 113 and in so doing it maintains the arm 125 of themicroswitch 126 depressed, so that the microswitch 126 will be closed.As a load is applied to the suction pads and the lifting unit lifts thedevice 24 together with the load gripped thereto by the action of thevacuum within the suction pads, the body 110 is lifted with respect tothe device 24 against the force of springs 122 until the stop element116 contacts the top wall 114. In this condition, the arm 125 ofmicroswitch 126 opens a circuit leading from the load releasepush-button 66 to the suction pads. When the device 24 is lifted and allthe time it remains lifted with the load suspended therefrom, the body110 of the safety system will remain spaced from the device 24 and willmaintain therefore the microswitch 126 in an open position so that, ifthe operator should erroneously depress the load release push-button 66,this would act only on the slow load lowering control and not on theload release device so that the load will slowly be brought into contactwith the ground. Once the load is at rest on the ground, a furtherlowering of the lifting cable will cause the body 110 of the safetysystem to be brought into contact with the frame 113 fastened to thedevice 24, both by gravity and by the force of springs 122. As the body110 bears on the frame 113, the lower end of body 110 will depress thearm 125 of microswitch 126 so that the circuit leading from the loadrelease push-button to the load releasing mechanism will be closed,thereby making this releasing mechanism active.

More particularly, as the body 110 is spaced from the device 24 andtherefore the microswitch 126 is opened, the sensor 48 pressed by theload will communicate vacuum to the suction pads and will begin to liftthe load. If the operator should depress the load release push-button,the latter instead of operating the release of the vacuum from withinthe sucton pads, will cause slow load lowering until the load is incontact with the ground, at which time the microswitch 126 is closed,thereby causing the vacuum to be released from the suction pads.

In order to provide versatility of the disclosed device, aninterchangeable suction pad holder is provided, as best shown in FIGS. 4to 8.

As seen in FIG. 4, the bottom of the device 24 is provided with asuction nozzle 209. Connected to this nozzle is a suction pad holder 210which is formed of a tubular frame 211 substantially rectangular inshape, which is provided at its corners and larger sides with connectors212 for securing suction pads 214. These connectors are preferablyattached to the holding frame 211 by welding. At the locations ofconnectors 212 the holding frame 211 is provided with holes 219 (FIG.6).

The suction pad holder 210 includes a preferably cup-shaped manifold215, having a flange 216 provided with holes 217 for securing thesuction pad holder to the device 24. The manifold 215 is provided on itsside wall with four holes 218 spaced apart by 90°, to each of which anend of a tube 213 is connected, the other end of which is welded to theframe 211 having in these locations holes 221 for communicating thetubes 213 to the frame 211.

The so formed suction pad holder is of a particularly strong and rigidstructure, capable of supporting the weight of the load to be liftedwith a remarkable degree of safety and of instantaneously communicatingthe vacuum to all the suction pads 214 through the holes 218 of themanifold 215, the tubes forming the frame 211 and the connectors 212. Inthis manner the vacuum is communicated to all the suction pads so thatthe load to be lifted can be firmly gripped by the six suction padssecured to the frame 211. By the provision of cutoff cocks 225 in thesuction pad connectors 212 it is possible to disconnect from the vacuumsource the suction pads not necessary for use so that the device 24 canoperate with four or two suction pads. This is advantageous where theweight of the load to be lifted is light, thereby avoiding sources ofpotential vacuum loss.

Alternatively, a valve or sensor 70 for each suction pad 46 (FIG. 9) canbe provided, which is normally held in a closed position in which thevacuum is cutoff, each suction pad being provided with an associatedcontrol element opening the valve when the associated suction padcontacts the load to be lifted.

As a further alternative, the tubular frame 211 can include valvingmeans cutting off one or more suction pads and operated by controlelements provided within device 24.

In FIG. 7 a suction pad holder is shown, the frame 211a of which issecured to the manifold 215a in a rotatable manner. To this end, theframe 211a has along its center line a tube 213a provided with a suctionpad 214 and in communication with the other tubes forming the frame. Themanifold 215a is provided with a pair of tubes 222 exiting from oppositeends and extending to center pins 223 whose function is to rotatably andtightly mount the frame 211a of the suction pad holder.

This suction pad holder lends itself very well to lift loads having asmall thickness and a large surface, for instance iron sheets, where thesuction pad holder must be applied on the lateral surfaces of the sheetsfor transport convenience.

Many changes and modifications can be made to this invention, andspecifically one or more components which are housed within the devicecould be located within the balancing assembly 18 in order to reduce theextra weight to be lifted.

I claim:
 1. In a lifting and/or transporting apparatus for lifting andcontrollably supporting a load by vacuum, said apparatus being of thetype including a device supporting at least one suction pad adapted tosealingly contact a load to be lifted, means for connecting a source ofvacuum to said suction pad to cause said suction pad to grip the load,means for lifting said device, and means mounted on said device forselectively releasing the vacuum in said suction pad and therebyreleasing the load, the improvement wherein said device comprises:meansfor measuring the vacuum in said suction pad; means, operable inresponse to measurement by said measuring means, for controlling theoperation of said lifting means; a body connected to said lifting meansand mounted to extend into said device for vertical movement relativethereto; biasing means operable for urging said device in a firstdirection relative to said body into a first position in abutmenttherewith; whereby, in the absence of a load and upon operation of saidlifting means, said biasing means urges said device into said firstposition, and upon the presence of a load and operation of said liftingmeans, said device moves by the weight of the load in a second directionopposite to said first direction and away from abutment with said body;and said body including means for, upon said device being moved in saidsecond direction, interrupting operation of said releasing means andthereby for preventing a lifted load from being released inadvertently,said interrupting means being inoperable when said device is in saidfirst position in abutment with said body.
 2. The improvement claimed inclaim 1, wherein said controlling means comprises first transducer meansfor operating said lifting means to raise said device when the vacuummeasured by said measuring means is at a first level, and secondtransducer means for operating an alarm when the vacuum measured by saidmeasuring means is at a second level lower than said first level.
 3. Theimprovement claimed in claim 2, wherein said second transducer meansfurther is operable to cause said lifting means to slowly lower saiddevice upon measurement by said measuring means of said second level. 4.The improvement claimed in claim 2, further comprising timer means forretarding operation of said second transducer means for a predeterminedtime period after measurement by said measuring means of said secondlevel.
 5. The improvement claimed in claim 1, further comprising stopmeans on said body for limiting movement of said device in said seconddirection.
 6. The improvement claimed in claim 1, wherein said bodyincludes a smaller size portion extending into said device and a largersize portion abutting said device in said first position, said smallerand larger size portions defining therebetween a step.
 7. Theimprovement claimed in claim 6, wherein said biasing means comprisevertical recesses in said larger size portion of said body, boltsextending into said recesses and having inner ends threaded into saiddevice, and compression springs surrounding said bolts and compressedbetween inner ends of said recesses and outer ends of said bolts.
 8. Theimprovement claimed in claim 1, wherein said releasing means includes amicroswitch having an actuating arm in engagement with said body.
 9. Theimprovement claimed in claim 1, further comprising a pad holderremovably mounted on said device and supporting a plurality of saidsuction pads, said pad holder comprising a vacuum manifold, means forremovably connecting said manifold to said device with said vacuumsource connected to said manifold, a tubular frame connected to saidmanifold with the interior of said frame in communication with saidmanifold, and connectors mounting said pads on said frame andcommunicating with said interior.
 10. The improvement claimed in claim9, further comprising valve means for selectively interruptingcommunication of vacuum to selected said pads.
 11. The improvementclaimed in claim 10, wherein said valve means are located at saidconnectors.
 12. The improvement claimed in claim 10, wherein said valvemeans comprise control elements in said pads operable to opencommunication to said source upon said pads contacting a load to belifted.
 13. The improvement claimed in claim 9, wherein said tubularframe is pivotally connected to said manifold.